Researchers at the University of Louisville School of Dentistry have headed a study that may explain how tobacco smoke contributes to gum disease.

"We have known that smokers are more likely to get gum disease and more likely to develop the plaque buildup that contributes to gum disease, but the clinical conundrum has always been why do they actually have less of the inflammation in and around their gums that we normally see in gum disease," said David Scott, PhD, associate professor of oral health and systemic disease research at UofL and lead investigator. "Our study sought the answer or answers to that question."

The study involved researchers from UofL, the School of Dentistry at Ege University in Turkey and Lund University in Sweden. It examined at saliva samples from smokers and non-smokers both with and without gum disease.

"We looked for molecules in the saliva samples that come from the bacteria that cause gum disease," Scott said. "We found that tobacco smoke appears to induce changes to one of these molecules, lipopolysaccharide, or LPS. LPS normally induces inflammation in our gums but in smokers LPS is altered in such a way that fails to stimulate inflammation.

"When this happens, the inflammatory and immune system is less able to deal with these gum pathogens and so gum disease develops," Scott said.

In fact, by the time many of these patients start to have symptoms, their disease can be fairly advanced and may be less responsive to current treatments, he added.

The researchers compared saliva samples from 54 patients, including 22 smokers with gum disease, 15 smokers without gum disease, 15 non-smokers with the disease and 14 non-smokers without the disease. The patients were treated at Ege University School of Dentistry.

The next step will be to investigate why the body's inflammatory and immune system does not recognize LPS from oral bacteria in smokers and to see if gum disease may develop differently in smokers than in nonsmokers.

It may be that researchers will then be able to develop different prevention and treatment strategies for cigarette smokers, Scott said.

Scott and his team recently received a five-year, $1.8 million grant from the National Institutes of Health to continue the work. UofL funded the original study.

Early publication of the results was in the November online issue of the Journal of Dental Research.